When a prisoner from a maximum security facility in America was told how little time children spend outside on average around the world, he replied: "Wow, that is depressing. That really is."

PersilPrisoners get two hours to be outside every single day.

To mark the launch of the campaign, OMO and Persil released a film in which prisoners from Wabash Valley Correctional Facility in Indiana, America, talk about the importance they place on their daily outdoors time.

"You have time to feel the sun on your face, it's everything to me," said one inmate, who volunteered to take part in the project.

"It's the most important part of my day. I take my frustrations and problems and leave them out there.

"If it was one hour a day? I think that would build more anger, it would be torture."

Persil

"We were shocked when we discovered that children today were enjoying as little time outside as prisoners," said James Hayhurst, global equity director of OMO and Persil.

"That's why we decided to make 'Free The Kids', to bring this issue to life and to start a global conversation about the importance of play for children's learning and development.

"It has also prompted us to think about ways we can help families rediscover outdoor play, both at home and through schools."

'Free The Kids' has been launched in partnership with Sir Ken Robinson, a global speaker and author who specialises in creativity, innovation and education.

Sir Robinson will take the role of chair of the Dirt Is Good Child Development Advisory Board, alongside Dr Stuart Brown, founder of the National Institute of Play.

The Board will investigate the best ways to help children play, explore and get dirty every day, so that they can learn and develop to their full potential.

The campaign will be asking parents to share their views on play and sign their child’s school up to Outdoor Classroom Day via the newly created www.dirtisgood.com.